As a part of a network switch, a router, or another network device, a line card (LC for short) can be used to connect a cable or an optical fiber.
In the prior art, a line card generates an optical bit stream, and then outputs the generated optical bit stream by using an optical fiber. Bandwidth of an optical fiber is a fixed value. For example, bandwidth of an optical fiber is 40 gigabits per second (Gb/s for short) or 100 Gb/s. Bandwidth of the optical bit stream output by the optical fiber is a fixed value. The foregoing technical solution is difficult to be applied to a flexible Ethernet.